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Y1 IMS > DNA, Structures And Replication > Flashcards

DNA, Structures And Replication Flashcards

1
Q

How do we know DNA is the molecule of life

A

Griffith
Avery
Hershey and chase
Experiments in 1920-50

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2
Q

How is DNA structured

A

Antiparallel strands form double helix
Sugar phosphate backbone
Base pairs join complementary strands by hydrogen bonding

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3
Q

What are the complimentary base pairs of DNA

A

Adenine with thymine

Guanine with cytosine

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4
Q

What is a nucleotide

A

Base
Sugar
And phosphate

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5
Q

What are the differences between base pair bonding

A

2 bonds between adenine and thymine

3 bonds between guanine and cytosine

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6
Q

What is the larger scale packing of DNA

A

Tightly coiled around histones to form chromatin with tightly coiled ones brain more active genes

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7
Q

How is DNA semiconservative

A

Each new double stranded molecule contains an original template strand and a newly synthesised complimentary strand

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8
Q

How is DNA synthesised

A

Starts at Origin of Replication
Utilises dynamic structure of the replication fork
At the replication fork:
Helicases unwind double strand
Single strand binding proteinase stabilise denatured DNA
DNA primase synthesises RNA primer allowing replication to start
DNA polymerase carries out the elongation of the new strand of DNA, formed by the complimentary base pairing to the template strand

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9
Q

What are the two strands of DNA

A

Leading and lagging strands

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10
Q

What direction does DNA synthesis happen in

A

5’ to 3’ so requires a free 3’ OH to add on from

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11
Q

What are Okazaki fragments

A

Short pieces of new DNA made on the lagging strand, sealed by DNA ligase

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12
Q

What do the two types of DNA polymerase do

A

DNA polymerase 1 replaces the RNA primers with DNA

DNA polymerase 111 adds new nucleotides to the new strands of dna

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13
Q

How are errors in replication amended and what is the resulting error frequency

A

DNA polymerase has a 3’- 5’ editing function to remove incorrectly inserted bases
This reduces error frequency to around 1 in 10^7

Other enzymes check too and reduce overall error frequency to 1 in 10^9

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14
Q

What causes mutations in DNA

A

Arise spontaneously due to errors in replication

Induced by DNA damage such as radiation damage or chemical

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15
Q

What are mutagens

A

Agents which induce mutations

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16
Q

What are the different types of gene mutation

A

Base substitution
Deletion of bases
Insertion of bases
Rearrangement of bases

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17
Q

What are the consequences of DNA mutation

A

Can be inherited if in germ cell

In somatic cell, could lead to cancer specifically of in stem cells

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18
Q

How can DNA be repaired

A

Base excision repair: proteins cut out damaged bases
Nucleotide excision repair: cut out sections of damaged DNA strand
DNA polymerase 1 replaces DNA by copying intact strand and DNA ligase seals it

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19
Q

What is a Barr Body

A

women inactivate one copy of their X chromosome in each cell and it is pushed to the edge of the nucleus

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20
Q

What is synteny

A

Where long strands of DNA sequences are present in the same order across species

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21
Q

What is translocation and what can it cause

A

Chromosome breakage and reforming

Can cause: disease, cancer, developmental abnormalities and can be inherited

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22
Q

What does Xist do?

A

A regulatory RNA that switches off a copy of the X chromosome in XX cells

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23
Q

What are exons and introns

A

Exons are coding sections of pre-mRNA

Introns are regions which are spliced out of pre-mRNA

24
Q

What are genes used for

A

Transcribed into Structural RNA or regulatory RNA

Transcribed into mRNA which is translated into proteins

May not contribute to making us, but are remnants of past events

25
Q

What is a retrovirus

A

RNA virus which infect cells and have reverse transcriptase which allows them to revert to DNA and join with our genome upon infection

26
Q

What are pseudogenes

A

Sequences that are common with functional human genes but are non-functional

27
Q

What are VNTRs

A

Variable number tandem repeats

Short sequences which are repeated multiple times

28
Q

What are SNPs

A

Single nucleotide polymorphisms

29
Q

What is a polysome

A

An RNA molecule that is covered in ribosomes

30
Q

What are lysosomes

A

Full of degradative enzymes which degrade certain molecules imported into the cell and old or damaged cellular components

31
Q

What do the ER and Golgi apparatus do

A

Various processes including the packaging and secretion of proteins

32
Q

What are the characteristics of mitochondria

A

The sites of energy generation in the cell by burning fuel to make ATP

Small circular chromosome inside them

Inherited mitochondrial DNA from mother

33
Q

What is a TATA box

A

Promoter region to initiate transcription

Short run of thymine and adenine

25 base pairs before start of transcription

34
Q

How is transcription initiated

A

Promoter region -> transcription factors bind -> RNA polymerase II binds-> some transcription factors disassociate -> transcription begins

35
Q

What is the difference between eukaryotes and prokaryotes

A

No nucleus in prokaryotes

Prokaryotes have polysistzonic rna which can code for multiple proteins in one strand of RNA sequence

36
Q

What does the 5’ cap do

A

Protects the mRNA from degradation

Helps with transcription

37
Q

How does a eukaryotic mRNA look

A

5’ cap -> non coding sequence -> coding sequence -> non coding sequence -> polyA tail

38
Q

What is polyadenylation

A

Transcription continues past the point where one or more poly A sequences are present, then stops

mRNA is then cut near the poly A sequence and a poly A tail is added

39
Q

What is splicing

A

Removal of intronic sequences from pre-mRNA

40
Q

What are locus control regions

A

Isolated promoter regions far away from the desired gene

41
Q

What are the three stop codons

A

UAA
UAG
UGA

42
Q

What is the start codon

A

AUG methionine

43
Q

What forms the Rough Endoplasmic Reticulum

A

membranes with bound ribosomes

44
Q

What are the two types of ribosomes

A

cytosolic

membrane-bound

45
Q

How is the translated sequence signalled to be a secretory protein

A

first part of sequence is a stretch of around 20 hydrophobic amino acids
this is a signal sequence

46
Q

Why do ribosomes then bind with to the endoplasmic reticulum

A

signal recognition particles bind to the signal sequence, causing the ribosome to dock to the ER

47
Q

What its the result of ribosome binding to the ER

A

the newly synthesised protein is fed through a channel into the lumen of the ER as it is translated,
the amino terminal signal sequence is usually cut off

48
Q

What happens with transmembrane proteins

A

Translation/ translocation continues until a stretch of ~20 consecutive hydrophobic amino acid is made ( a transmembrane domaine) This is embedded in the membrane, The ribosome continue to make the rest of the membrane in the cytosol

49
Q

What happens in the ER

A

Disulphide bridges form

Sugar side chains added

50
Q

What happens in the Golgi apparatus

A

Some ER sugars are trimmed and replaced

51
Q

How are mitochondrial proteins made

A

deposited in cytosol
post-translational import
Chaperone binds to protein to prevent folding allowing it to be posted into mitochondria
mitochondrial targeting sequence at end of protein to promote import into mitochondria

52
Q

What are TOM and TIM of the mitochondria

A

Two channels which the protein destined for mitochondrial matrix is threaded through
Translocase of the outer membrane (TOM)
Translocase of the inner membrane (TIM)

53
Q

What is cancer

A

A group of diseases
Solid tumours and leukaemias
Disease of body’s own cells

54
Q

What is are key features of cancer at the cellular level

A

uncontrolled cell division
change in morphology
dedifferentiation of cells
Cell migration into adjacent and distant tissues

55
Q

What is the progression through cancers for cells

A

Normal cells -> hyper proliferative cell population -> early adenoma -> late adenoma -> carcinoma

56
Q

What are the three types of environmental factors that can cause cancer

A

Biological
chemical
physical

57
Q

What does an epidemiology study show

A

That a chemical is carcinogenic in human

Looks for an association between the exposure and cancer

Y1 IMS (9 decks)

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